This invention relates to polymers having polyethylenic backbones with pendant ethylenically unsaturated groups that undergo addition polymerization upon exposure to suitably active radiation and/or chemical initiation.
The use of organic polymers in coating compositions for application on a wide variety of substrates such as floor materials, appliance housings, paper products, etc., is well known. Characteristically, such polymers are often either thermoplastic or thermosettable. For many coating applications, the thermoplastic polymers do not exhibit the necessary resistance to abrasion and organic solvents. Unfortunately, the heat curable, thermosettable polymers are usefully applied only to substrates that can tolerate the temperatures often required to cure such polymers. In addition, thermal curing processes are often too time consuming to be economical in many applications.
Thus, it has been desirable to develop polymers which cure by non-thermal means such as by moisture cure or radiation cure techniques. Moisture curable polymers are often unsatisfactory because of the restrictions of temperature and relative humidity necessary to achieve a crosslinked coating. Also, the time period required to achieve complete cure (two to three weeks) is often impractical.
Polymers, which upon exposure to light or comparable radiation source crosslink to form insoluble materials, exhibit the most desirable properties in that they generally are cured rapidly and can be applied to heat sensitive substrates. Accordingly, such radiation curable polymers are often useful in coating applications as varnishes and inks as well as finish coats on flooring and other items such as counter tops. Such applications usually require that the resulting insoluble, crosslinked coating be non-yellowing, abrasion resistant and stain resistant.
Unfortunately, many of the conventional radiation curable polymers, such as epoxy acrylates, now being employed in conventional, UV curable varnish and ink formulations are particularly sensitive to light, especially sunlight, in that they yellow and craze after relatively brief periods of exposure. Other conventional radiation curable compositions contain very toxic substances such as monomeric or unreacted isocyanate, hydroxyalkyl esters of acrylic acid and the like. Examples of conventional radiation curable and photo curable polymeric materials are described in U.S. Pat. Nos. 3,928,299 and 3,924,033.
In view of the aforementioned deficiencies of conventional radiation curable polymeric compositions, it is highly desirable to provide a relatively nontoxic substance which crosslinks readily and quickly upon exposure to low doses of relatively low energy radiation and/or chemical initiation to form a crosslinked coating exhibiting long-term toughness, abrasion resistance and stain resistance.